A laser confocal microscope disclosed below in Patent Literature 1, for example, has been proposed as a laser confocal microscope (a microendoscope) which uses an image guide fiber composed of a plurality of optical fiber element wires. A microendoscope system proposed in Patent Literature 1, for example, transmits fluorescence generated by exciting an observation target with one photon through an image guide fiber and enables the generated fluorescence to be observed.
When an image captured by such a fluorescence observation system (i.e., a fluorescence image) is observed, it is important to specify where a position of a surface or a position of a focus of an observation target is. Non-Patent Literature 1 described below discloses a method for specifying a position of a surface or a position of a focus of an observation target by applying an image recognition technology to a fluorescence image obtained using a field-of-view (FOV) type fluorescence microscope.